Stimulating investment in pearl farming in ... - World Fish Center

Water Temperature and Cyclone Frequency in the Pacific: Implications for Pearl Farming Final, June 2008°C, respectively (Pouvreau and Prasil 2001). The water temperature in Mangareva Lagoon,situated even further south and to the east (23° 10’S, 134° 95’W), varies from 21.3 - 28.8 °C(Pouvreau and Prasil 2001). During El Niño years, the water temperature in TakapotoLagoon may reach 31.5 °C (Pouvreau et al. 2000b). In November 1985, vertical temperatureprofiles were measured over a 3 day period in Rangiroa Lagoon (Rougerie 1985). Theseindicated that the temperature of the water down to a depth of 30 m was similar to that atthe surface.In other parts of the world, black-lip pearl oysters are cultured in water with much morevariable temperature regimes. For example, at culture sites at Dongonab Bay, Sudan andKabira Bay, Japan temperatures range from 21 – 34 °C and 17 – 30 °C, respectively (Reed1966; Sugiyama and Tomori 1988).The temperature ranges reported above suggest that black pearl farms are either located inareas where the water temperature is outside the optimum temperature range or that theoptimum ranges in other countries differs markedly from that in north-east Australia.2.3.2 Silver Pearl FarmsCSIRO Marine Research (2003) has compiled coastal ocean temperature statistics for variouslocations off the West Australian coast, including two silver-lip pearl oyster farms located inRoebuck Bay near Broome (18° 2’ S) and Whalebone Island in Exmouth Gulf (22° 11’ S),respectively. The mean monthly sea temperature varied from 21.4 °C (July) to 30.9 °C(January) in Roebuck Bay and from 19.5 °C (August) to 29.7 °C (February) in Exmouth Gulf(Figure 2a). These data are based on measurements taken over different study periods andat different depths (1992 to 1998 near the seabed in 12 m of water in Roebuck Bay versus1994 to 1998 and 1 m above the seabed in about 6 m of water at Whalebone Island) and arenot therefore directly comparable. The water temperature at a silver-lip pearl farm in KuriBay, Western Australia ranged from 25-32 °C (Pass et al. 1987).The temperature ranges reported above suggest that some Western Australian silver pearlfarms are located in areas where the minimum water temperature is below the lower limit ofthe optimum temperature range and that some are situated in areas where the maximumwater temperature is close to the upper limit of the optimum range.2.3.3 Other Locations2.3.3.1 Northern AustraliaCSIRO Marine Research (2003) has also compiled coastal ocean temperature statistics forthree other locations off the North West Australian coast. The mean sea temperature rangesfor these locations are depicted in Figure 2b and are as follows:• Barrow Island (20° 48’ S) - 21.6 °C in August to 29.0 °C in March, with temperatures at adepth of 15 m similar to those on the surface;• Osprey Bay at Ningaloo Reef (22° 14’S) - 22.2 °C in August to 27.1 °C in March at a depthof about 5 m.;• Entrance to Shark Bay (26° 8’S) - 20.9 °C in October to 23.8 °C in March/April).It should be noted that the temperatures at the entrance to Shark Bay are unlikely to berepresentative of the Bay itself, because of the influence of strong tidal flows (CSIRO MarineResearch 2003).The Ecology Lab Pty Ltd – Marine and Freshwater Studies Page 5